1. Field of the Invention
The present invention concerns a device to generate brilliance levels on a display screen. This device can be used to make a so-called static correction and/or a so-called dynamic correction of homogeneity defects in the screen.
As is known, certain types of display screens comprise a set of cells: each cell is a portion of the screen defined by the intersection of a so-called row electrode with a so-called column electrode. A control voltage is applied to each cell which is then capable of emitting light. The quantity of light emitted by a cell is measured, for example, in terms of luminance. The luminance is a function of the control voltage, according to a curve, hereinafter called a characteristic, which depends on the specific qualities of the screen at the cell considered.
Prior art methods for manufacturing display screens are aimed at obtaining screens that are as homogeneous as possible. As a first approximation, it can be considered that a single characteristic is valid for the entire screen. However, it is sometimes necessary to consider different characteristics for various parts of the screen.
As is known, a screen characteristic takes the following form:
below a threshold voltage, there is no transmission of light;
then the luminance increases with the control voltage;
from a saturation voltage onwards, the luminance is constant and keeps a maximum value; this characteristic therefore defines a range of luminance.
2. Description of the Prior Art
There are known methods to apply discrete, control voltage values, making it possible to obtain degrees of luminance, hereinafter called brilliance levels.
A prior art device, marketed under the reference HV01 and made by the firm SUPERTEX, is capable of delivering discrete voltage values that are evenly spaced out.
This device, applied to the electrodes of the different cells of a display screen according to a method that shall be explained below, generates brilliance levels. Unfortunately, owing to the shape of the characteristic, these brilliance levels are very poorly distributed over the luminance range.